Fast ion beams are of interest for various applications including production of radioactive isotopes, neutron production, radiography, fusion, and various forms of radiation therapy. Beams of fast ions are typically produced in accelerators of various configurations such as cyclotrons or synchrotrons. Accelerators are relatively large and expensive machines that are costly to run and maintain.
The development of very short pulse lasers that are capable of providing extremely high intensities and electric fields, has stimulated research in exposing matter to laser light electric fields to generate therefrom fast ions. In a laser based accelerator, a high intensity laser beam is focused on a target which contains the elements of the ions that are being accelerated, the laser interacts with the target, ionizes it and accelerates the ions. A number of articles and patent documents have described such methods of using lasers to provide relatively inexpensive fast ion sources. For instance, U.S. Pat. No. 6,906,338 for “Laser driven ion accelerator” to T. Tajima describes, using laser pulses “having a pulse length between approximately 1 to 500 femtoseconds (fs)” focused to energy densities of between about 1018 to about 1023 W/cm2 to produce a high flux of energetic ions such as protons, that may be used for medical purposes. The pulses are directed to interact with targets of various designs and provide radiation components that “include different species of ions (e.g., protons), x-rays, electrons, remnants of the pulse 102, and different energy components (e.g., MeV, 10's MeV, and 100's MeV within a certain energy band or window)”. International Patent Application No. WO 2010/070648 for “A System for Fast Ions Generation and a Method Thereof” to some of the inventors of the present application, describes a system and method for generating a beam of fast ions. The system comprising: a target substrate having a patterned surface, a pattern comprising nanoscale pattern features oriented substantially uniformly along a common axis; and; a beam unit adapted for receiving a high power coherent electromagnetic radiation beam and focusing it onto said patterned surface of the target substrate to cause interaction between said radiation beam and said substrate, enabling creation of fast ions. Other articles are cited in the Background and General Description sections of WO 2010/070648.
Once such a high-energy beam of fast ions has been generated, it is necessary to select from it ions of the desired energy range required for the treatment to be performed using those ions, and also to direct the beam to the volume to be treated by the beam. The beam can be focused and directed by use of magnetic fields, but because of the very high magnetic fields required to divert high-energy ion beams, conventional electromagnets are extremely heavy, expensive, and require substantial energy in order to generate the required fields.
There therefore exists a need for a system and method for generating high magnetic fields for use in directing and shaping a high-energy ion beam, and for beam energy range selection, which overcomes at least some of the disadvantages of prior art systems and methods.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.